Process and apparatus for the production of tufted pile fabrics

ABSTRACT

Improved apparatus for producing tufted pile fabrics comprising a tufting machine having plural rows of needles and loopers wherein the loopers in a first row of loopers in the direction of travel of a backing sheet are longer than loopers of the next row so that yarn loops formed in the backing sheet by the first row of loopers are not displaced by the loopers in the next row to cause irregular formation of loops in the tufted fabric product; also, a process for producing pile fabrics of uniform pile height by a loop robbing technique.

United States Patent 1 Short Dec. 25, 1973 PROCESS AND APPARATUS FOR THE PRODUCTION OF TUFTED PILE FABRICS [75] Inventor: Joe T. Short, West Point, Ga.

[73] Assignee: Doering Milliken Research Corporation, Spartanburg, SC.

[22] Filed: Jan. 10, 1972 [21] Appl. No.: 216.630

[52] US. Cl. 112/79 A, 112/266 [51] int. Cl. D05c 15/22 [58] Field of Search 112/79 R, 79 A, 80, 112/266, 410, 439, 221

[56] References Cited UNITED STATES PATENTS 3,093,100 6/1963 Thompson 112/79 R 3,019,748 2/1962 Card 112/79 R 3,402,686 9/1968 Rodstein et a1. l 112/79 R 2,876,441 3/1959 Boyles 112/79 A 2,853,034 9/1958 Crawford 112/79 A 3,398,708 8/1968 Card 112/79 R Primary Examiner-James R. Boler Attorney-Norman C. Armitage et a1.

[57] ABSTRACT Improved apparatus for producing tufted pile fabrics comprising a tufting machine having plural rows of needles and loopers wherein the loopers in a first row of loopers in the direction of travel of a backing sheet are longer than loopers of the next row so that yarn loops formed in the backing sheet by the first row of loopers are not displaced by the loopers in the next row to cause irregular formation of loops in the tufted fabric product; also, a process for producing pile fabrics of uniform pile height by a loop robbing tech nique.

12 Claims, 10 Drawing Figures PATENTEDDECZSIQH same or 2 FIG. -5-

PROCESS AND APPARATUS FOR THE PRODUCTION OF TUFTED FILE FABRICS This invention relates to the production of tufted fabrics and, more particularly, to an improved process and apparatus for the production of tufted fabrics, such as carpets, upholstery, wall coverings and the like.

Conventional tufting machines for producing pile fabrics employ a needle bar containing a plurality of needles mounted therein. The needle bar extends across the width of a suitable backing sheet, and means are provided for moving the sheet past the needle bar while the bar is reciprocated to cause repeated penetration of the sheet by the needles. Continuous yarn strands are fed to the eyes of the needles and upon penetration of the needles through the backing sheet, the strands are engaged and retained by loopers positioned in a looper bar on the opposite side of the backing sheet. These loopers have hook portions which serve to hold the yarn strands carried by the needles and to form yarn loops on the face of the backing sheet as the needles are withdrawn from the sheet after each penetration.

The density of needles in the needle bar of a tufting machine is expressed in terms of gauge, i.e., the number of needles per linear inch of needle bar. To produce dense pile fabrics having a large number of pile loops across the length of the backing sheet, it is necessary to employ fine gauge, multi-needle tufting machines having a large number of needles per inch of length of the needle bar. To achieve this density of needles along the needle bar, the needles are located in plural rows on the bar with the rows spaced in the direction of movement of the backing sheet and with the needles in each row staggered with respect to the needles in each other row. In like manner, the corresponding loopers in the looper bar are located in staggeredrow relation so that individual needles remain provided with individual loopers cooperating therewith to form the yarn loops.

In machines having multiple-row needles and loopers, particularly those used for producing very fine gauge, low loop, dense fabrics, problems are presented because of the necessary compact arrangement of the needles and loopers. Quite often, yarn loops formed by a first row of needles and loopers are swept or pushed backwards against the face of the moving backing sheet by the backs of the hooks of the next row of loopers. This displacement of the loops causes them frequently to be pushed back into the path of travel of the needles of the first needle row and results in the displaced loops being sewn through during the formation of a subsequent row of loops. This condition is referred to as chain stitching or sew through.

Also, the displaced loops frequently are contacted and pushed by the points of the needles during their downward stroke resulting in irregularly long loops being formed with yarn pulled, or robbed, from previously formed adjacent loops which themselves become irregularly short. This condition is commonly referred to as tagging" Problems in machine design are also presented due to the close spacing required of the loopers and their retaining set screws in the looper bar.

It is therefore a primary object of the present invention to provide an improved tufting machine which overcomes the aforementioned and other problems encountered in the production of tufted pile fabrics.

A further object of this invention is to provide an improved process for producing pile fabrics of uniform pile height by a loop robbing technique.

Briefly, the invention involves providing a multiple needle tufting machine having plural rows of needles and loopers, wherein loopers in a first row of loopers in the direction of travel of the backing sheet are longer than the loopers of the next subsequent row so that the hooks of the loopers in the first row are closer, or nearer, the backing sheet than the hooks in the next row of loopers. In this manner, the loops formed by the needles and looper elements of the first row are not contacted by the backs of the hook portions of lower positioned looper elements in the subsequent row, thereby preventing the loops from being swept back or displaced, and avoiding irregular formation of the loops in the tufted fabric product.

The above as well as other objects of the present invention will become more apparent from the following detailed description and drawings, in which:

FIG. I is a schematic side elevation view of the needle and looper bar mechanisms of a conventional tufting machine for producing pile fabrics, and showing the components for feeding yarn and a backing sheet past the needle and looper bar components during formation of a tufted pile fabric;

FIG. 2 is an enlarged perspective view of a portion of the needle and looper bar of the tufting machine of FIG. 1;

FIG. 3A is a sectional view of a portion of a backing sheet with a row of yarn loops shown inserted therein in normal position in a loop pile fabric;

FIG. 3B is a sectional view of a portion of a backing sheet with the yarn loops shown therein in displaced condition as a result of chain stitching or sew through;

FIGS. 4 and 5 are sectional side elevation views of the conventional needle and looper bar mechanisms shown in FIG. 2, with the needle bar shown in different positions or reciprocation;

FIGS. 6 and 7 are sectional side elevation views of a needle bar and looper bar mechanism of the present invention, with the needle bar shown in positions of reciprocation corresponding to that of FIGS. 4 and 5, respectively;

FIG. 8 is a sectional side elevation view of a modified needle bar and looper bar mechanism of the present invention; and

FIG. 9 is a perspective view of the looper shown in FIG. 8.

Referring more specifically to the drawings, FIG. 1 is a schematic side elevation of the needle and looper bar mechanisms of a conventional tufting machine which includes a needle bar 10 supporting a plurality of needles arranged in plural rows ill, 12 extending along the length of the bar and spaced in the direction of movement of a backing, or base, sheet 14. Suitable means, such as driven rollers 16, 18 are provided for advancing the backing sheet past the needle bar, and the sheet is supported adjacent the needles by a throat plate, or needle plate 20.

A warp sheet of yarns 22 is fed to the needles of the needle bar by driven feed rolls 24, and individual yarn strands of the sheet are threaded through the eyes of the individual needles, as shown. Needle bar 10 is supported for reciprocation by a linkage mechanism 26 having a sleeve or journal bearing 28 eccentrically mounted on a rotatable shaft 30 which is driven to cause the needles to repeatedly penetrate the backing sheet 14 for insertion of the yarn strands into sheet 14.

Positioned below backing sheet 14 is a looper mechanism which includes a looper bar 36 containing a plurality of rows 32, 33 of loopers correspondingly positioned along the looper bar for operative cooperation with the individual needles. The looper bar and loopers are supported on a shaft 34 for oscillation into and out of engagement with yarn strands carried by the needles. The loopers have hook portions which extend in the direction of movement of the backing sheet and hold the strands to form yarn loops as the needles are withdrawn from the backing sheet 14, and which pivot to readily release the loops for advancement of the backing sheet prior to a subsequent loop-forming operation.

As best shown in FIG. 2, the needles and loopers of corresponding rows ll snd 32 are positioned in staggered relation along the bars and 30, respectively to those needles and loopers in corresponding rows 12 and 33. When the needle bar it) is in its lowermost position of reciprocation, as shown, the needles penetrate the backing sheet (not shown), and the looper bar 30 is pivoted to a position wherein hook portions 42 of the loopers engage the yarn strands, one of which 44 is shown, carried in the eyes of the needles. Hooks 42 retain the yarns during upward reciprocation of the needle bar as the needles are withdrawn from the backing sheet to form a pair of rows of yarn loops extending transversely across the backing sheet.

When needle bar It is in its upmost position of reciprocation with the needles retracted from the backing sheet, looper bar 30 and the loopers pivot rearwardly relative to their position in FIG. 2 so that hooks 42 of the loopers, which have their tips extending in the direction of movement of the backing sheet, release the yarn loops just formed. Backing sheet 14 advances in the direction indicated by the arrow A (FIGS. 1 and 2) and the needle bar reciprocates downwardly to initiate another loop forming cycle. This sequence is repeated as the backing sheet continues to advance so that individual needles of the needle bar form a plurality of yarn loops, such as shown in FIG. 3A, extending longitudinally along the length of the backing sheet. As seen in FIG. 2, alternate needles in needle bar 10, and their corresponding alternate loopers are positioned to form rows ll, 12 and 32, 33, respectively, spaced in the direction of movement of the backing sheet, in order to obtain a high density of yarn loops across the width of the backing sheet.

As heretofore mentioned, problems are encountered in the use of fine gauge tufting machines having pluralrow needles and loopers. FIG. 4 is a side sectional elevation of the conventional needle and looper bar mechanism of FIGS. 1 and 2 and illustrates the position of the needles and loopers during completion of a pair of second loops 52, 54 in a backing sheet 55. As the nee dles approach their upper position out of backing sheet 55, adjacent loopers 56, 58 in the two rows on the looper bar 30 are in upright position retaining the yarn strands to form the loops 52, 54.

As best seen in FIG. 5, as the needle bar 59 begins its downward motion the loopers 56, 58 pivot to the left to release the loops 52, 54. Due to the closeness of the loopers, the back of the hook of looper 56 contacts and displaces loops 52 and 60, previously formed by looper 58, into the path of downcoming needle 62. The tip of needle 62 thus passes through the loop portion of one or more of the loops 52, 60 and creates undesirable chain stitching" of the loops, as is shown in FIG. 38. Alternatively, the tip of needle 62 may not pass through the previously formed loops 52, 60, but may strike one of the yarn strands, pushing it downwardly during further downward movement of the needle and causing additional yarn to be pulled from the previously formed loop to produce irregularly long and short loops in the fabric. To prevent these undesirable occurrences, the present invention provides a needle and looper mechanism construction as shown in FIGS. 6 and 7.

As best seen in FIG. 6, the loopers 76 in the first row of loopers in the direction of movement of the backing sheet 74 are longer than the loopers 78 in the following row of loopers. The hook portions 80 of loopers 76 are thus closer to the path of the backing sheet 74 than the hook portions 82 of the loopers 78. Correspondingly, to accommodate the new positions of the loopers and provide yarn thereto, the needles in the first row of needles in the direction of movement of the backing sheet are shorter than the needles 72 in the following row of needles. This positions the tips of the needles 72 closer to the path of the sheet 74 than the needles 70 in the first row.

Thus as seen in FIG. 7, as needle bar 84 begins its downward motion, the loopers 76, 78 pivot to the left to release the loops 85, 86. Since the hook portions 82 of loopers 78 lie further from the backing sheet 74 than the hook portions of the front row of loopers 76, they pass well below the tips of the loops 85, 88 formed by the front row loopers 76. Since the loops 85, 88 lie above the maximum height of the looper 78, they are not displaced or swept backwardly to interfere with the path of movement of needles 7G in the front row of the needle bar.

It can be appreciated from the foregoing description and FIGS. 6 and 7 that the loops formed by the shorter loopers 78 initially will be longer than those formed by the longer loopers 76 because of their greater distance from the backing sheet 74. To provide a pile fabric of uniform loop height, the process of forming the loops is accomplished by a loop robbing technique. To explain, during each cycle of reciprocation of the needle bar to simultaneously form two rows of yarn loops in the base sheet, a uniform amount of yarn is fed to the needles by feed rolls 24 (FIG. 1). Control of these rolls 24 is accomplished by conventional means, well known in the art, and will not be described in detail herein. Since the amount of yarn supplied by the feed rolls 24 to the row of longer needles 72 and shorter loopers 78 is the same as that supplied to the needles and loopers 70, 76 (FIGS. 6 and 7), it is necessary that an additional amount of yarn be supplied from some source to provide for the larger loops 36 which must be formed by the loopers 78. This additional amount of yarn is drawn back from the longer loops previously formed by the loopers 78, thus shortening the loops (shown as 90 in FIGS. 6 and 7) to the desired height of the loops 85, 88 formed by the row of loopers 76. In this manner, during each stitch cycle, as two rows of yarn loops are simultaneously formed in the base sheet by co-action of the two rows of needles and loopers, the front row of loops in the direction of movement of the base sheet will be shorter than the subsequent row of loops; however, during the simultaneous formation of the next two rows of yarn loops in the base sheet, the length of the longer loops in the previously formed higher row of loops is shortened automatically to the length of the loops in the other previously formed row of loops to provide a uniform length of loops in the base sheet.

In the method of the present invention, the additional yarn necessary to form the row of longer loops may be withdrawn from the previously formed row of longer loops at any desired period of the stitch cycle,i.e., the loop forming operation, by adjusting the tufting machine settings in conventional manner. For example, yarn may be withdrawn or robbed from the previously formed row of long loops during downward movement of the needles into the backing, upward movement of the needles out of the backing, or during both such directions of reciprocation of the needles.

FIG. 8 discloses modified forms of both the needle and looper mechanisms of the present invention. Due to the close spacing of the loopers in the looper bar and the desirability of having the loopers readily removable for replacement or repair, the base or main portions of the looper elements are held in the looper bar by set screws, as shown at 100 in FIG. 2. In view of the very close spacing of the loopers in the bar of very fine gauge tufting machines, it is difficult to design and construct the bars and the retaining set screws to the close tolerances required. To reduce the number of fastening means and to facilitate the construction of the looper bar, the modified form of looper mechanism shown in FIGS. 8 and 9 is provided. As seen, two yarn strandengaging looper means are formed of a single piece of metal, or the like. Two hook portions 92, 93 extend from a single main body portion 94 which is retained by a single set screw 96 in a slotted portion of the looper bar 98. First hook portions 92 of each of the looper mechanisms are located in alignment in a first row along the bar and second hook portions 93 of each of the looper mechanisms are aligned in a second row along the bar which is below and rearwardly of the first hook portions 92 in the direction of movement of the backing sheet. As best seen in FIG. 9, the hook portions 92, 93 will be staggered along the length of the bar by an angled leg portion 99 of hook portion 92 which extends outwardly at about a 45 angle from the main body portion 94 of the looper mechanism. With this construction of two hooks on a single main body portion of the looper mechanism, it can be seen that the number of set screws and receiving slots required to maintain the loopers in the looper bar can be reduced by one half. Also, the thickness of the retaining shank, or main body portion of the mechanism can be maintained at a minimum.

As previously described and shown in FIGS. 6 and 7, when the needle bar means comprise a single needle bar 84, the needles in row 72 are longer, or extend further below the bar, than the needles in row 70 in order to operatively cooperate with and provide yarn strands to the row of shorter loopers 78. If desired, however, plural needle bars 101, 102 (FIG. 8) having different paths of reciprocation, may be provided to position the different rows of needles at different depths of penetration in the backing sheet to accommodate the rows of loopers of different height.

From the foregoing detailed description, it can be appreciated that the unique needle bar and looper mechanism of the present invention provides an improved tufting machine for producing pile fabrics, and is of particular value in the production of narrow gauge dense pile fabrics requiring the use of multiple row needle and looper bars.

That which is claimed is:

1. In a multiple needle tufting machine for producing loop pile fabrics and carpets having plural rows of needles and a looper bar containing corresponding plural rows of cooperating loopers having hooks extending in the direction of movement of the backing sheet, the needles and hooks of corresponding rows being staggered transversely to the direction of movement of the backing sheet with respect to the other corresponding rows, which machine would on occasion be subject to unsatisfactory operation in the production of such products due to tagging and sew through; the improvement wherein the hooks of the loopers in a first row of loopers in the direction of movement of the backing sheet are positioned further from the looper bar than the books of the loopers in the next row, whereby in operation tagging and sew through are substantially eliminated as a result of the yarn loops formed by the first row of loopers passing freely beyond the loopers in the next row.

2. In a multiple needle tufting machine for producing loop pile fabrics and carpets having reciprocating needle bar means containing plural rows of needles and looper bar means containing corresponding plural rows of loopers, the needles and loopers positioned respective on opposite sides of the path of movement of a backing sheet and the loopers having their hooks extending in the direction of movement of the backing sheet to operatively cooperate with the needles to form yarn loops therein, and further the needles and hooks of corresponding rows being staggered transversely to the direction of movement of the backing sheet with respect to the other corresponding rows, which machine would on occasion be subject to unsatisfactory operation in the production of such products due to tagging and sew through; the improvement wherein a first row of loopers in said looper bar means in the direction of movement of the backing sheet are positioned closer to the path of the sheet than the following row of loopers whereby yarn loops formed by the first row of needles and loopers pass without interference with the operation of the following row of needles and loopers.

3. A machine as defined in claim 1 wherein the tips of the needles in the first row of needles corresponding to said first row of loopers are positioned further from the path of the backing sheet than the tips of the needles in the following row of needles.

3. A machine as defined in claim 2 wherein an adjacent pair of loopers in said first and said following rows together comprise a main body portion removably secured to said bar and a hook portion positioned between said bar and the path of the backing sheet, said hook portion including first hook means positioned in said first row of loopers adjacent the backing sheet path and second hook means positioned in said following row of loopers at a greater distance from the backing sheet path than said first hook means.

5. A single piece looper means adapted for use in a multiple needle tufting machine for producing loop pile fabrics and carpets comprising a main body portion adapted to be retained in and extend outwardly from a looper bar of the tufting machine, and a hook portion extending therefrom and including first and second hook means positioned in spaced planes generally paraliel to said main body portion, with outer extremities of said first and second hook means positioned in spaced planes perpendicular to said first mentioned plane, whereby said looper means when used in such a tufting machine forms loops which pass freely and substantial tagging and sew through are avoided.

6. Looper means as defined in claim wherein one of said hook means is positioned in a common plane with said main body portion.

7. Yarn engaging means for use in a tufting machine for producing loop pile fabrics and carpets and comprising a support bar, a plurality of looper means mounted in spaced relation along the length of the bar and each consisting of a single piece composed of a main body portion attached to and extending outwardly from the bar, and first and second hook portions located outwardly of said main body portion, first hook portions of said looper means aligned in a first row along said bar and said second hook portions aligned in a second row along said bar spaced from said first row, the hook portions in one of said rows positioned a greater distance from said bar than the hook portions in said other row and all of the hooks extending in the same direction.

8. Means as defined in claim 7 wherein hook portions in said first row are positioned in staggered relation to hook portions in said second row along the length of the bar.

9. A method of forming a loop pile fabric comprising the steps of providing a base sheet, simultaneously forming two adjacent rows of yarn loops in the base sheet with the loops of one row longer than the loops of the other row, subsequently simultaneously forming two rows of yarn loops in the base sheet and reducing the length of the loops in the previously formed row of longer loops to the length of the loops in the other previously formed row of loops.

10. A method of forming a loop pile fabric comprising the steps of providing a base sheet, feeding uniform lengths of yarn to two rows of needles extending across the base sheet, reciprocating the yarn-carrying needles through the sheet while retaining the inserted yarn lengths by loopers to form a pair of rows of yarn loops with the loops of one row longer than the loops of the other row, farther feeding said uniform lengths of yarn to the needles, longitudinally advancing the base sheet, and reciprocating the yarn-carrying needles through the sheet, retaining the inserted yarn lengths with the loopers to form rows of yarn loops, and withdrawing yarn from the yarn loops of the previously formed row of longer loops to conform them to the length of the loops in the other row of said pair.

11. A method as defined in claim 10 wherein yarn is withdrawn from the previously formed row of longer yarn loops during movement of the needles into the base sheet.

12. A method as defined in claim 10 wherein yarn is withdrawn from the previously formed rows of yarn loops during movement of the needles out of the base sheet.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION December 25, 1973 Patent No. 678 Dated Inventor(s) J TQ Short It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On Title Page, Assignee should read --Deering-- instead of Doering".

Column 2, line 40, the word "or" should read --'of--.

Column 3, line 18, the word snd should read --and--.

Column 6, line 51, the number "3" should read --4--.

Signed and sealed this lrth day of June l9 7L (SEAL) Attost:

EDWARD M.FLETCHER,JR. c. MARSHALL mun Attesting Officer Commissioner" of Patents ORM P0-1 (10 69) USCOMM-DC 6O376-P69 U.5. GOVERNMENT PRINTING OFFICE 2 '99 0-355-334, 

1. In a multiple needle tufting machine for producing loop pile fabrics and carpets having plural rows of needles and a looper bar containing corresponding plural rows of cooperating loopers having hooks extending in the direction of movement of the backing sheet, the needles and hooks of corresponding rows being staggered transversely to the direction of movement of the backing sheet with respect to the other corresponding rows, which machine would on occasion be subject to unsatisfactory operation in the production of such products due to tagging and sew through; the improvement wherein the hooks of the loopers in a first row of loopers in the direction of movement of the backing sheet are positioned further from the looper bar than the hooks of the loopers in the next row, whereby in operation tagging and sew through are substantially eliminated as a result of the yarn loops formed by the first row of loopers passing freely beyond the loopers in the next row.
 2. In a multiple needle tufting machine for producing loop pile fabrics and carpets having reciprocating needle bar means containing plural rows of needles and looper bar means containing corresponding plural rows of loopers, the needles and loopers positioned respective on opposite sides of the path of movement of a backing sheet and the looPers having their hooks extending in the direction of movement of the backing sheet to operatively cooperate with the needles to form yarn loops therein, and further the needles and hooks of corresponding rows being staggered transversely to the direction of movement of the backing sheet with respect to the other corresponding rows, which machine would on occasion be subject to unsatisfactory operation in the production of such products due to tagging and sew through; the improvement wherein a first row of loopers in said looper bar means in the direction of movement of the backing sheet are positioned closer to the path of the sheet than the following row of loopers whereby yarn loops formed by the first row of needles and loopers pass without interference with the operation of the following row of needles and loopers.
 3. A machine as defined in claim 1 wherein the tips of the needles in the first row of needles corresponding to said first row of loopers are positioned further from the path of the backing sheet than the tips of the needles in the following row of needles.
 4. A machine as defined in claim 2 wherein an adjacent pair of loopers in said first and said following rows together comprise a main body portion removably secured to said bar and a hook portion positioned between said bar and the path of the backing sheet, said hook portion including first hook means positioned in said first row of loopers adjacent the backing sheet path and second hook means positioned in said following row of loopers at a greater distance from the backing sheet path than said first hook means.
 5. A single piece looper means adapted for use in a multiple needle tufting machine for producing loop pile fabrics and carpets comprising a main body portion adapted to be retained in and extend outwardly from a looper bar of the tufting machine, and a hook portion extending therefrom and including first and second hook means positioned in spaced planes generally parallel to said main body portion, with outer extremities of said first and second hook means positioned in spaced planes perpendicular to said first mentioned plane, whereby said looper means when used in such a tufting machine forms loops which pass freely and substantial tagging and sew through are avoided.
 6. Looper means as defined in claim 5 wherein one of said hook means is positioned in a common plane with said main body portion.
 7. Yarn engaging means for use in a tufting machine for producing loop pile fabrics and carpets and comprising a support bar, a plurality of looper means mounted in spaced relation along the length of the bar and each consisting of a single piece composed of a main body portion attached to and extending outwardly from the bar, and first and second hook portions located outwardly of said main body portion, first hook portions of said looper means aligned in a first row along said bar and said second hook portions aligned in a second row along said bar spaced from said first row, the hook portions in one of said rows positioned a greater distance from said bar than the hook portions in said other row and all of the hooks extending in the same direction.
 8. Means as defined in claim 7 wherein hook portions in said first row are positioned in staggered relation to hook portions in said second row along the length of the bar.
 9. A method of forming a loop pile fabric comprising the steps of providing a base sheet, simultaneously forming two adjacent rows of yarn loops in the base sheet with the loops of one row longer than the loops of the other row, subsequently simultaneously forming two rows of yarn loops in the base sheet and reducing the length of the loops in the previously formed row of longer loops to the length of the loops in the other previously formed row of loops.
 10. A method of forming a loop pile fabric comprising the steps of providing a base sheet, feeding uniform lengths of yarn to two rows of needles extending across the base sheet, reciprocating the yarn-carrying needles through the sheet while retaining the inserted yarn lengths by loopers to form a pair of rows of yarn loops with the loops of one row longer than the loops of the other row, farther feeding said uniform lengths of yarn to the needles, longitudinally advancing the base sheet, and reciprocating the yarn-carrying needles through the sheet, retaining the inserted yarn lengths with the loopers to form rows of yarn loops, and withdrawing yarn from the yarn loops of the previously formed row of longer loops to conform them to the length of the loops in the other row of said pair.
 11. A method as defined in claim 10 wherein yarn is withdrawn from the previously formed row of longer yarn loops during movement of the needles into the base sheet.
 12. A method as defined in claim 10 wherein yarn is withdrawn from the previously formed rows of yarn loops during movement of the needles out of the base sheet. 